Pi Compute Module
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Glen Walker (2585) 469 posts |
RISC OS built into an NEC display? https://www.raspberrypi.org/blog/compute-module-nec-display-near-you/ I have been dreaming of creating a board that would take the Compute Module and turn it into an upgrade-able micro computer for quite a while now (basically a Compute Module, SATA or mSATA on board and all the connectors on the back-edge to allow for a neat little case). Essentially it would get around the fact that the existing Pi has connectors coming out all over the place. I guess the trick would be to get it small, working and cheap enough for general users to buy. Then I also guess that the 700MHz ARMv6 is probably not really great for most of the user base (who realistically would end up running Linux on it…). Maybe I could build it into a keyboard? :—) How compatible is RISC OS Pi with ARMv6 in the Compute Module? I wonder if future versions with have an ARMv8 like the Pi 3…? |
Chris Evans (457) 1614 posts |
Fully:-) IIRC RISC OS need slight tweaking because the EMMC behaves slightly different to an SD card. n.b. I think NEC are only going to offer it on their 40"+ monitors aimed at video signage etc. It would be nice in all monitors and TVs! |
Jeffrey Lee (213) 6048 posts |
Yes, I believe there’s a BCM2837 version of the compute module in the works.
I doubt they’d offer it for their consumer models. SBCs are small and lightweight enough for people to be able to easily mount them to the back of a TV/monitor themselves. In the office we’ve even used velcro to attach small computers (mac minis and similar) to the back of TVs. |
Steve Pampling (1551) 8155 posts |
Odds on you could fasten a Pi or beagle to the mount bracket points with four strips of Meccano. |
Glen Walker (2585) 469 posts |
Yeah I can definitely see the logic behind NECs decision. A couple of jobs ago we used to use a Pi strapped to the back of a TV to display a corporate video at trade shows. The TV we used had a built-in video player but it had a massive delay every time the video looped through whereas the pi just kept it looping without any pause. |
Alain Lowet (7745) 41 posts |
My dream would be to rebuilt an adaptor board (with 74LVC245) to interface with the podule expansion connector of my real Archimedes 440, dropping my old motherboard and replacing with this one (The compute module has enough GPIO ports to get datas and addresses at good place, adding also other necessary signals)… Then, the trick would be to reimplement software to use existing podules… |
Steve Pampling (1551) 8155 posts |
Ah, now there you hit difficulties. The motherboard circuit diagrams are available via “Chris’s Acorns” if I remember correctly, so replicating that functionality is a electronic engineering task. USB to IDE interface for your disc drive. Then your problem with figuring out what the code is in/with the podule boards and making it 32bit or reverse engineering the whole podule and building an equivalent. Of course you could just emulate the 440 on a Pi, and mount the Pi inside the 440 case. |
Dave Higton (1515) 3497 posts |
Alain, what existing podules would you like to use? There would be no point in doing it for USB, RS-232, SCSI or a printer port, for example. In fact I can’t right now think of any existing podule that would be useful. I hope you will enlighten me! (MIDI is on its way.) |
Rick Murray (539) 13806 posts |
You will need, I think, 42 GPIO lines to support a basic IOC podule. But that’s not the hard part. The hard part is going to be sorting out the timing and how those signals behave with respect to each other. That’s why early machines talked to the IOC and the IOC talked to the podules. In this way, one writes bytes to word aligned addresses and these become podule accesses.
Let’s ignore the 32 bit issues and look instead at how you would:
I could sort of imagine allocating some memory in the podule address range and having it abort when accessed which your abort handler will use to talk to the podule via GPIO and pass up the data as if actual hardware was used, but I don’t see how you can assure that the timing of everything is bang-on. Remember, your podules will be relying upon the timing provided by the host. So I’ll echo Dave and repeat:
…
Does RISC OS work with a USB to parallel port dongle? And to reply to something much earlier:
At work we have a fairly recent laptop running Ubuntu plugged into a big flat panel TV (something in the order of 40"). It provides employee information and promotional stuff in a sort of Powerpoint slideshow. And to the top… NEC have a 98" monitor. Which translates to two metres sixteen by one metre twenty one (screen size), with a resolution of 3840×2160 (60Hz). Or, to ram home the size of that thing: [looks at pictures shown: ho ho, what is that – Skytree and Omi Jingu?] |
Dave Higton (1515) 3497 posts |
Nobody uses a printer through a parallel port these days. |
Tristan M. (2946) 1039 posts |
Gutter strapping is probably cheaper than Meccano. Let’s be honest. I like the idea of a compute module based board. I tried something like it with a Pi zero with a right angle GPIO header, which was plugged into a strip board prototyping HAT, which also had an RTC, OLED, and I2S DAC. |
Rick Murray (539) 13806 posts |
Oh, I’m sorry. I must have missed the RISC OS drivers for the plethora of USB printers available these days… |
Dave Higton (1515) 3497 posts |
And if someone really did want to start using a parallel printer port, it would be far more sensible to use GPIO pins directly, and write a replacement Parallel module. This would be far easier and have much more chance of working correctly. |
Elesar (2416) 73 posts |
Such as this one?
…on the resources tab on the above linked product page. |
Steffen Huber (91) 1949 posts |
There are the same drivers available as in the good old parallel times. Whatever Gutenprint supports, and PCL and PostScript. And, IIRC, there was a USB-parallel adapter available for the IYONIX back in the Castle days. Again IIRC, I think it worked fine for all printers supporting the SPP, but not those that needed EPP/ECP or other bidirectional stuff. |
Andrew Conroy (370) 725 posts |
Is there a list of those printers which are known to work via the GPIO-Parallel adaptor but which don’t work through a USB-Parallel adaptor? From first-hand experience I do know that USB-Parallel adaptors are still being bought (and used) both by RISC OS and non-RISC OS users for use with legacy parallel port printers. |
Chris Evans (457) 1614 posts |
Lexmark still make at least one current model printer (mono laser with PCL & PostScript) that has a parallel port! |
Dave Higton (1515) 3497 posts |
Colour me amazed that people are still using parallel ports. Nevertheless, if someone’s starting with a Raspberry Pi, I still think it makes sense to use the GPIO pins and an appropriate Parallel module. My original question to Alain Lowet still stands unanswered: what existing podules would you like to use? |
Tristan M. (2946) 1039 posts |
Of course it would need USB driver support, but I just spent a good 20 seconds on AliExpress to search for “USB parallel port” and found quite a few adapters for around $AUD5. |
Andrew Conroy (370) 725 posts |
Most ‘well behaved’ USB-Parallel adaptors are already supported, aren’t they? Plug one in and up pops a window from !Printers asking you which Printer Definition File you’d like to use with it |
Alain Lowet (7745) 41 posts |
The compute module has 45 lines available to do the task of connecting a simple podule (without B pins), 2,4,8 Mhz will be produced by an external oscillator on the interface board along with the necessary 74LVC245 to make the level transitions. |
Alain Lowet (7745) 41 posts |
By the way, i found a very interesting Compute Host board by waveshare wich is extended in regards of the original RPI one, and contains lot’s of goodies that could be useful at a time (e.g. an ardion uno compatible connector, ADC’s, RTC clock…) |
Rick Murray (539) 13806 posts |
Nostalgia is a powerful thing (I say, listening to an online radio station that only plays music from the ‘80s (hmm, I wonder if they’ll ever play anything by Jackson ever again?)). However you are going to have to accept some compromises as technology moves on. For instance, forget ADFS floppies. USB drives can’t understand them. Wait, hang on… User ports, MIDI… You don’t mean the AKA10 do you? That thing was MASSIVE! |
Alain Lowet (7745) 41 posts |
Oh, yes, and i totally forgot an important point for me, as you know, the Broadcom Soc is a very versatile computing device, the GPIO’s can be programmed in several ways (a least five different mode are supported), and, on the other hand, i like also the DIN41612 connectors available on the podule bus, that are real connector contrary to all those ‘end of cards’ connectors. So my idea is to use the middle line of the connector to pass specific signals from the Broadcom CPU, to open the way for designing new cards… Trying to have: best of both worlds :-) |
Alain Lowet (7745) 41 posts |
and…yes…i admit, AKA10 is on my list ;-) |
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